This invention relates to an improved container for the cryopreservation of mammalian cells and particularly for the long-term cryopreservation of red blood cells. The cryopreservation, or freezing, of red blood cells is a relatively recent development in the medical area. One of the processes used for the freezing of red blood cells is described in U.S. Pat. No. 4,018,911 which describes a method of freezing red blood cells using hydroxyethyl starch (HES) as a cryoprotectant. This patent however, does not address the problems associated with providing an appropriate blood compatible container which incorporates the particular characteristics needed for freezing with liquid nitrogen.
One commercially available bag for cryopreservation of blood components is made by Gambro. Its utility for red blood cell cryopreservation is limited, however, because the spike ports protrude and can be damaged at liquid nitrogen temperatures. The presence of these parts usually require these bags to be stored in metal containers, thereby using valuable space in the storage cabinets. If one removes the protruding parts at any time, the integrity of the bags content is compromised.
Ideally, a container for cryopreservation in liquid nitrogen should have a number of properties. It should 1) not break or leak at any time during the process, 2) allow for rapid, easy insertion and removal of a spike during transfusion, 3) provide a flat transfusion port so that a large quantity of these containers can be stored without metal frames which require a lot of additional space, and 4) all spike ports, including the transfusion port should be designed in such a manner as to eliminate protrusions which could break off at low temperatures during handling In addition, since the containers will be frozen in liquid nitrogen and stored in liquid nitrogen vapor, it should have low nitrogen permeability and good low temperature properties.